Specimens of Bolbosoma capitatum and Bolbosoma sp. were recovered from 2 male Physeter macrocephalus that died following a mass stranding on Prince Edward Island, Canada. Some aspects of previous descriptions of B. capitatum have been incomplete, particularly with characteristics of the hooks of the proboscis being poorly defined. Females of B. capitatum were found to have 16-18 longitudinal rows of hooks with either 7-8 or 8-9 hooks in each row. The largest hooks with strongly curved blades were apical to median (overall range 69-112 micro m long), whereas the basal hooks were spinelike (68-91 micro m long). The basal hooks had a unique transverse orientation of the roots, an attribute apparently shared only with B. physeteris, among the 14 species of Bolbosoma from cetaceans and pinnipeds. Although Bolbosoma capitatum had apparently been reported from P. macrocephalus in the eastern Atlantic Ocean, none of these records could be substantiated. The current report constitutes a new geographic record (Gulf of St. Lawrence, Canada) and the first account of this parasite in sperm whales from North American waters..